De Gea is yet to join up with his new team-mates, but he is due to jet to America over the weekend and could be handed an immediate opportunity to impress in United's friendly date with the Seattle Sounders.
Ferguson, who is also waiting for England U21 international Phil Jones to arrive in the States, said: "Obviously De Gea joins us in Seattle, along with Jones, so it will be good to get them involved right away as we're not too far away from the start of the season, so we've a bit of work to do there.
"They are the future of the club. The likes of Chris Smalling, Jones and Jonny Evans - we've got the three best centre-backs in the country, young ones.
"I watched the England U21 games against Spain and they did very well. I had five players, including De Gea, in the game, so it was of interest to me.
"That's what we're always trying to achieve, a foundation. And we have one that's very strong."